Vortex-antivortex arrays (VAA) that are created in a type-II superconducting film by lattices of ferromagnetic dots with perpendicular anisotropy have been investigated. The highest critical current is ... [more ▼]

Vortex-antivortex arrays (VAA) that are created in a type-II superconducting film by lattices of ferromagnetic dots with perpendicular anisotropy have been investigated. The highest critical current is shifted to a nonzero value of the applied field, and current-voltage characteristics show different regimes of vortex motion even in zero-applied field due to the presence of the VAA. Creep of interstitial vortices is observed at low driving forces. This flux creep is strongly field-polarity dependent. [less ▲]

We performed ac susceptibility measurements to explore the vortex dynamics and the flux-pinning properties of superconducting Pb films with an array of microholes (antidots) and not fully perforated holes ... [more ▼]

We performed ac susceptibility measurements to explore the vortex dynamics and the flux-pinning properties of superconducting Pb films with an array of microholes (antidots) and not fully perforated holes (blind holes). A lower ac shielding together with a smaller extension of the linear regime for the lattice of blind holes indicates that these centers provide a weaker pinning potential than antidots. Moreover, we found that the maximum number of flux quanta trapped by a pinning site, i.e., the saturation number n(s), is lower for the blind hole array. [less ▲]

The influence of a periodic landscape of pinning sites on the vortex dynamics in Pb thin films is explored by ac susceptibility measurements. For different amplitudes h of the ac drive, the ac ... [more ▼]

The influence of a periodic landscape of pinning sites on the vortex dynamics in Pb thin films is explored by ac susceptibility measurements. For different amplitudes h of the ac drive, the ac susceptibility chi=chi'+ichi" exhibits a complex field dependence associated with different dynamic regimes. At very low ac drives where both multiquanta vortices trapped by the antidots and interstitial vortices oscillate inside the pinning potential (intravalley motion), a small kink in chi'(H) together with a very low dissipation is observed. At intermediate ac excitations such that vortices in the antidots remain pinned, whereas interstices are driven out of the pinning well, a more pronounced kink in the screening coinciding with the onset of dissipation [chi"(H)not equal0] indicates the entrance of interstitial vortices. Eventually, at high enough amplitudes all vortices are set in motion and the penetration of interstitial vortices appears as a sudden reduction of the shielding power. We show that these distinctive features allow us to identify clearly the maximum number of flux quanta per hole, regardless of the vortex dynamic regime. [less ▲]